Modern computers are typically made up of a number of components which together form a complete computing system. For example, in addition to the central processing device and main memory, a given computer system may include separately housed tape drives, disk drives, or power supplies, with each such device being a separate and distinct component. Although such components are separate and distinct from one another, they are typically configured for modular insertion in a larger assembly, such as a structurally rigid frame, or cabinet. The cabinet thereby accommodates the easy insertion and removal of the individual devices for repair and replacement.
To the extent that the system allows for the easy insertion and removal of modular devices, it is necessary to consider the means by which the devices are shielded against EMI. Such EMI shielding is of particular concern when any one of the devices in the cabinet may be removed while other devices in the cabinet are still running. In other words, one particular concern is making sure that if any one of the devices is removed, while the others are still operating, the EMI shield for those devices still operating is not broken.
One approach to creating individual shielding for modular circuit boards is disclosed in U.S. Pat. No. 4,868,716, issued to Taylor on 19 Sep. 1989. In particular, Taylor discloses enclosing modular circuit boards within a five-sided enclosure. According to Taylor, shielding for the sixth side is provided by the top grounding plane of a base circuit board, a gasket made of an elongated strip of spring metal material, and a socket assembly made of fence strips and a metal insert. Accordingly, the provision of shielding on the sixth side in the Taylor device involves the use of these multiple components, which, at some point, are assembled together to implement the shielding approach.
What is needed, however, is a shielding approach for the modular components of a computer system which is reliable, inexpensive, and relatively straightforward to implement. More specifically, what is needed is an effective EMI shielding approach which uses as few components as possible.